Disk drives are commonly used in workstations, personal computers, laptops and other computer systems to store large amounts of data in a form that can be made readily available to a user. In general, a disk drive comprises a magnetic disk that is rotated by a spindle motor. The surface of the disk is divided into a series of data tracks. The data tracks are spaced radially from one another across a band having an inner diameter and an outer diameter. Each of the data tracks extends generally circumferentially around the disk and can store data in the form of magnetic transitions within the radial extent of the track on the disk surface.
An interactive element, such as a magnetic transducer, is used to sense the magnetic transitions to read data, or to transmit an electric signal that causes a magnetic transition on the disk surface, to write data. The magnetic transducer includes a read/write gap that contains the active elements of the transducer at a position suitable for interaction with the magnetic surface of the disk.
As known in the art, the magnetic transducer is mounted by a head structure to a rotary actuator arm and is selectively positioned by the actuator arm over a preselected data track of the disk to either read data from or write data to the preselected data track of the disk, as the disk rotates below the transducer. The head structure includes a slider having an air bearing surface that causes the transducer to fly above the data tracks of the disk surface due to fluid currents caused by rotation of the disk.
In modern high capacity disk drives, the spindle motor is arranged to mount a stack of axially aligned storage disks, with the storage disks in the stack being spaced from one another. The use of multiple disks increases the total disk surface available for the storage of data. A head stack assembly comprises a stack of actuator arms, each mounting a head or a pair of heads. The stack of actuator arms is arranged adjacent the stack of storage disks with each head being positioned by the respective actuator arm over the surface of a corresponding one of the disk surfaces. The spacing between any two opposed disks of the stack is sufficient to accommodate the placement of an actuator arm between the two disks of the stack to position each of a pair of heads opposite the surface of a respective one of two opposing disks in the stack.
A complete assembly of the head stack assembly and the stack of disks is called a head disk assembly. Typically, the spindle motor and head stack assembly are mounted on a mounting surface of a base plate to form the head disk assembly. The spindle motor is mounted on the mounting surface at a location that is proximate one end of the base plate and the head stack assembly is mounted at a location proximate the other end of the base plate. A cover having a top and side portions extending downwardly from the top, is received over the spindle motor and head stack assembly, and is secured to the outer perimeter of the base plate to form a housing comprising the base plate and the top and side portions of the cover. In this manner, the housing encloses the spindle motor and head stack assembly of the head disk assembly in a protected environment.
The height of the head disk assembly, from the mounting surface of the base plate to the top most storage disk of the disk stack, must have a dimension that fits within the spacing between the base plate and the top of the cover. Typically, the extremities of the height dimension of each of the spindle motor and the head stack assembly exceed the extremities of the height dimension of the stack of disks. This is because the spindle motor mounts the disk or disks and has a greater height so that it can be mounted to the base plate at one end, and receive a clamp or other mechanical element at the other end, to secure the disk or disks to the spindle motor. In addition, the actuator structure must place an actuator arm/head assembly both above the top most disk surface and below the bottom most disk surface of the stack of disks to permit the reading and writing of data from these surfaces. Thus, the extremities of the spindle motor and head stack assembly dictate the overall height of the disk drive housing. In conventional disk drive products, the spacing between the top of the cover and the base plate is maintained at a dimension suitable to fit the entire head disk assembly, over substantially the entire width and length of the disk drive housing.
A disk drive product also includes various electrical connectors to couple the disk drive to a host computer (i.e. the computer that is using the disk drive to store data). The connectors include a host connector, to form electrical paths for the transmission of commands and data between the disk drive and the host computer, and a power connector, to connect the disk drive to the power supply of the computer to energize the motors and circuits within the disk drive.
A printed circuit board (PCB) is mounted on the side of the base plate opposite to the side mounting the head disk assembly. The PCB is used to mount control electronics for controlled operation of the spindle motor and actuator arm positioning. The PCB also includes read/write channel and disk controller circuitry coupled to the read/write heads, to control the transfer of data between the data tracks of the storage disks and the host connector. In a conventional disk drive, the PCB is generally rectangular in shape and has width and length dimensions that are approximately equal to the width and length dimensions of the base plate.
Moreover, a set of support posts is arranged to extend downwardly from the base plate for use in securely mounting the disk drive within the host computer.
The total height, width and length of the connectors, base plate, PCB and cover of the disk drive must fit within a mounting space provided in the host computer. Thus, the smaller the overall dimensions of the disk drive, the less space required within the host computer to accommodate the drive. The trend in recent years has been to design and build disk drive products with high data storage capacities, but that are lightweight and compact in size to minimize the space requirements and weight addition imposed on computer systems using the disk drives for data storage.
In one recent proposal, the overall dimensions of the disk drive are reduced by providing several PCB segments and mounting the PCB segments within cutout portions formed in the disk drive housing. The PCB segment approach takes advantage of miniaturization of integrated circuits to implement PCB structures in less than the full length and width dimensions of the disk drive. However, this arrangement incurs added power requirements for transmission of signals between PCB boundaries and does not fully realize economic use of available space.